In 1482, Quasimodo was about 20 years old. Claude Frollo had turned 36. The priest was still involved in the education of his younger brother, Jehan. But this project had caused him bitterness. Jehan had grown up to be wild, lazy, and ignorant. He was more interested in having fun than in studying. This saddened his older brother. He threw himself even more into the study of science. As a priest, he became more learned and more severe. As a man, he became sour and gloomy.
Dose it mean: the teaching of his brother and the responsibility he had for educating him.